A four-high roll stand consisting of two upright housings with work and back-up rolls and with roll bending devices for the work rolls are known to the art from West German DE patent publication 22 50 953. In such roll stands the chocks of the work rolls are located between vertical blocks anchored in the windows of each housing. The work rolls are deflected at their ends for roll crow control by double acting piston cylinder roll bending units carried by intermediate members which are contacted by the chocks. Each vertical block affixed to an associated housing is designed to support the intermediate members which can slide vertically in the window of the stand. Each intermediate member is provided with two sets of horizontal rails which extend parallel to the rolls adjacent the axes of the work rolls through and between the operating and drive side housings for the purpose of supporting the chocks during roll changing. This means that as many as four such rails may be employed. The vertical blocks affixed to the housings have vertical guides that project towards the inner members which are equipped with corresponding grooves. With the aid of this roll stand construction the work rolls can be adjusted both vertically and displaced horizontally over a wide range.
This construction makes it possible to more quickly change the work rolls as a unit than previous systems without the need to disconnect the hydraulic system for the roll bending piston cylinder assemblies. Part of this was accomplished by later designs in which the vertical blocks affixed to the housing were equipped with piston cylinder units which positioned and supported the work roll chocks and moved the chocks in such a way that the elevation of the rails carried thereby were brought in line with the receiving surface or tracks of a roll change rig arranged on the operator side in front of the window of the mill stand. Some of the above referenced characteristics are disclosed in U.S. Pat. Nos. 3,736,785 and 4,543,870.
This construction and referenced elements found necessary to change the work rolls set in the above described mill arrangement possessed some serious disadvantages, particularly in the employment and location of the chock supporting rails and in mills employing means for moving the work rolls axially relative to each other, which will be more fully discussed below.
With reference to these shortcomings, it is the object of the present invention to greatly simplify the construction and number of elements necessary to change the work roll set in a rolling mill stand and wherein the employment of chock supporting members or rails in the location of the work rolls are not required. While the invention is particularly useful in mills for rolling strip wherein the work rolls are adjusted in opposite axial directions, it may find use in mills not having this feature.
It is another object of the present invention to provide an improved mill arrangement for effecting a roll change, by eliminating, to a large extent, the multiple arrangement of complicated roller or glide paths employed in the past in the area of the windows and by changing the upper and the lower work rolls a unit by employing only one set of rails arranged away from the roll bite. In a mill where the work rolls are axially moved relative to each other, this, in part, is accomplished according to the invention by providing a locking mechanism to firmly interlock the work rolls and their chocks to perform a roll changing, which during operation of the mill can be disengaged to permit relative axial roll movement.
The above objects are achieved by providing a work roll separator, preferably filled with an elastomer, in the lower work roll chocks, the free end of which supports the upper work roll chocks in such a way that they may be moved horizontally. Since the upper work roll chocks may be secured against sliding horizontally in relation to the lower work roll chocks, the work roll change can be executed in a new way, i.e. the two work rolls, arranged one above the other and interlocked in a stable manner, can be jointly pulled from the stand onto a roll change platform. The chock supporting rails which up to now had been required for the upper work roll can be eliminated.
Furthermore, the enlargement of the clearance in the area of the roll bite improves the procedure of threading the rolled strip through the mill, allows the system of guiding the strip into the entry area of the work rolls to be improved and enlarges the space for removing torn strips during a strip "wreck". The enlargement of the clearance of the roll stand in the roll bite area also simplifies the mounting of the spray headers, as well as that of the readjustment of the spray angle.
With the aid of the elastic work roll separators located in the lower work roll chocks, a secure stable support of the upper work roll on the lower work roll and the maintenance of the distance between them is assured and there is not required special monitoring. The roll separators filled with an elastomer, therefore, must only be constructed in such a way that it is sufficiently strong to bear the weight of the upper work roll and its chocks, without impairing compliance with conventional safety requirements. Due to the fact that the elastic separators in the lower work roll chocks function in conjunction with the locking device in one of the upper work roll chock, the two work rolls can be secured together as a unit as a compact structure for the roll change.
With reference to the locking device of the present invention, it is proposed to attach centering pieces to the upper free ends of the roll separator pistons, and as to one of the pistons of the drive side upper chock a bolt of the locking device can be pushed from above. The centering pieces of the separator pistons are received in longitudinal grooves cut into glide plates of the upper work roll chocks, which grooves are approximately the same length as the distance of the counter-directional horizontal movement of the work rolls. The centering pieces may be designed and made from a material allowing the upper work roll chocks to slide smoothly, although the pistons of the separators are constantly exerting a force on the upper work roll chocks. The centering pieces of the separator pistons provide additional assurance against unintentional movement of the work rolls toward each other during the roll change.
In still referring to the locking device, the bolt of the locking device associated with the one roll separator piston is installed in a vertical hole in the one upper work roll chock and can be adjusted to either a locking position or unlocking position, by means of a stationary actuator attached on the chock outside of the mill housing. The bolt of the locking device is constructed in such a way that it can latch through the glide plate into a recess in the centering piece of the work roll separator. If therefore, for example, the locking bolt is loosely installed in the vertical hole of the upper work roll chock, it can, based on its gravity, lock with the separator, thus interlocking the two work rolls. In order to change rolls, the work rolls need only to slide against one another to find the locking position.
As an additional feature of the disclosed roll locking device, the actuator is provided with a cylinder pin installed in the horizontal hole in the upper drive side work roll chock, with one end of the pin engaging the bolt by a special shaped portion, while its other end functions in conjunction with a latch device which provides at least two positions. The latch device consisting of a spring/ball arrangement functions in conjunction with two ring-shaped spaced apart grooves formed in the cylinder pin. This allows in a simple way for the installation of the locking bolt between two positions, which can be adjusted manually or by means of a hydraulic piston cylinder actuator for greater accuracy, the actuator being attached on the outside of the chock.
The positioning system for the locking bolt of the locking device can, if desired, be made part of the cylinder pin of the actuator by means of an opening in the locking bolt into which engages an offset tongue formed in the cylinder pin. The tongue of the cylinder pin may be surrounded by the inner walls of the opening in the locking bolt on all sides and the height of the offset of the connecting tongue is designed to correspond to the locking position or the unlocking position. In this way the locking bolt is guided by force and its position established with a minimum of mechanical clearance.
Another feature of the roll change system of the present invention is to provide the lower work roll chock in the lower area with glide bars or rollers, which in the locked position of the work rolls are brought into contact with glide rails. The glide rails are preferably attached to a vertical movable support carriage which can be moved against the lower work roll chocks by hydraulic piston cylinder units located in the vertical blocks affixed to the mill housing. In this way, the opening of the windows of the mill housings to effect roll changing is enlarged, as well as providing clearance in the roll bite area of the stand, so that more free space is available for removing and replacing of the work rolls, the spray headers, the guidance systems for the rolled product, etc.